PROJECT SUMMARY Despite the growing concern about poor sleep health in the US and high rates of comorbidity between sleep disturbance and mental illness, limited attention has been given to how the downstream effects of sleep disturbance may contribute to psychopathology. Given recent recognition of sleep disturbance as a potential transdiagnostic factor and links between sleep disturbance and OCD, it is critical to examine how the negative effects of sleep loss, such as decreased inhibition and increased stress, may contribute to and maintain OCD, as these processes may be novel targets for intervention. Aim I will examine whether acute sleep restriction causes decreased inhibition and increased OC symptoms in healthy sleepers. Aim II will examine whether those with OCD exhibit increased sleep disturbance and decreased inhibition compared to healthy controls and whether inhibition mediates the relationship between sleep disturbance and OC symptoms. Aim III will examine whether stress (including daily stressors and stress reactivity) amplify the negative effects of sleep disturbance. Consistent with the RDoC research framework, the proposed studies will utilize multiple levels of analysis, including self-report, objective sleep assessment, and behavioral tasks, and combine both experimental and correlational methods to examine sleep disturbance as a causal factor in OCD and the roles of inhibition and stress. The ultimate goal for this proposal is to integrate diverse lines of research across subfields into a unified model to identify transdiagnostic mechanisms that contribute to and maintain psychopathology. Specific training goals include developing expertise in the psychobiological assessment of sleep, inhibition, stress, and OCD, as well as training in quantitative methods to analyze variables relevant to psychopathology over time. The skills developed in integrating methods and theory from multiple subfields and utilizing multi-method approaches to assess transdiagnostic variables that contribute to and maintain psychopathology will provide a foundation for a successful career as a clinical psychological scientist.